This application claims the priority of Korean Patent Application No. 2003-0080575, filed on Nov. 14, 2003, in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of exposing a wafer using a scan-type exposure apparatus.
2. Description of the Related Art
In general, photolithographic processes are used to manufacture semiconductor devices. During the photolithographic process, a photosensitive film is coated on a wafer used to form a fine circuit pattern, a pattern of a predetermined shape formed on a mask is transferred onto the wafer by projecting light to the mask using an exposure apparatus. Thus, the pattern is formed on the wafer.
Recently, a scan-type exposure apparatus that performs exposure by moving a reticle and a wafer in opposite directions to each other has been developed as one of exposure apparatuses used in a photolithography technology to manufacture semiconductor devices.
In the scan-type exposure apparatus, to perform an exposure process, a reticle is moved in a certain direction while being fixed to a reticle stage in the lower portion of an illuminating system that projects light having a predetermined wave length. A projective optical system is disposed in the lower portion of the reticle stage. A wafer stage is disposed in the lower portion of the projective optical system. The wafer moves in the opposite direction to the reticle stage while being fixed to the wafer stage. The light generated by the illuminating system passes through the reticle and the projective optical system and reaches the wafer such that the exposure process is performed on a semiconductor chip formed on the wafer.
Typically, in the scan-type exposure apparatus, to expose one of exposure target areas on the wafer, i.e., one shot, a scanner initially undergoes acceleration and pre-scanning steps. In the acceleration step, the scanner is accelerated in the direction of scanning until the speed of the scanner reaches a desired scanning speed. In the pre-scanning step, the scanner is settled and leveled to stably scan the shot at a constant speed after termination of the acceleration step and before exposure of the shot and operates while controlling exposure conditions.
FIG. 1 is a view explaining a wafer exposing method in a scan-type exposure apparatus according to conventional art. Referring to FIG. 1, in the wafer exposing method according to conventional art, to expose a plurality of shots S that form an exposure target area 10 on a wafer W, an array of shots extended in a certain direction, e.g., a first shot column Sc1 that is formed of an array of shots S1, S2, S3, S4, S5, . . . extending in the x-direction, is first exposed. During exposure of the first shot column Sc1, the shots that form the first shot column Sc1 are each scan exposed sequentially in the y-direction indicated by arrows 12. After all of the shots of the first shot column Sc1 is exposed, shots that form a second shot column Sc2 that is adjacent to the first shot column Sc1 are each scan exposed sequentially in the y-direction in the same manner as the first shot column Sc1.
FIG. 2 is a view for explaining a scanner's scanning distance required for exposing shots formed on a wafer in the wafer exposing method described with reference to FIG. 1.
Referring to FIG. 2, according to conventional art, the scanner undergoes an acceleration section (distance a) and a pre-scanning section (distance b) and scan exposing a section (distance c) corresponding to a y-direction distance of a first shot S1. Then, the scanner further undergoes a post-scanning section (distance b) to move to a pre-scanning start position P, so as to start exposing a second shot S2 that is the next shot to be exposed. Here, the total scanning distance of the scanner for exposing two shots is equal to 4a+4b+2c.
The post-scanning section is not related to controlling the exposure conditions (in contrast to the pre-scanning section), and is simply intended to move the scanner to the pre-scanning start position P. Therefore, in the wafer exposing method according to conventional art, the post-scanning section that is not necessarily required for the exposure process in practice is added to the scanning distance of the scanner. As a result, the scanning distance for exposure and the amount of time required for exposing a semiconductor chip will substantially increase, causing degradation of productivity in the exposure process.